Pens of the type discussed here are known. They are used for administering a medication to a patient. They are frequently designed such that the patient can perform the administration himself by means of the pen. The carpule for such pens has a chamber that is closed by a moveable stopper. By moving the stopper, the medication is driven out of the chamber and administered to a patient. This includes pens with a drive that is used to move the stopper within the chamber, preferably by a specific path, in order to administer a defined volume of a medication. It has been found that the size of the pen significantly limits the comfort of using such an application means. Therefore, pens that are designed relatively small are preferred. This has the drawback that this means only a limited quantity of a medication is available.